R 中 igraph 网络的输出 shapefile [英] Output shapefile for the igraph network in R

问题描述

你好，我在 R 中有一个使用 igraph 库的网络

Hello I have a network in R using the igraph library

Vertices: 616 
Edges: 6270 
Directed: TRUE 
No graph attributes.
Vertex attributes: name, Lat, Lon.
Edge attributes: V3.

如何使用顶点中的纬度、经度信息为顶点和边生成两个 shapefile?

How can I generate two shapefiles for the Vertices and the Edges using the Lat, Lon info in the vertex?

推荐答案

您可以使用 sp 和 maptools 包执行此操作.maptools 中有一些方便的函数 writePointsShape() 和 writeLinesShape() 可以写入 ESRI shapefile 格式.

You can do this using the sp and maptools packages. There are handy functions writePointsShape() and writeLinesShape() in maptools that will write to the ESRI shapefile format.

在此之前，需要从图形顶点中提取纬度/经度信息并将其放入顶点的SpatialPoints对象和SpatialLinesDataFrame对象中对于边缘.

Before doing this, it is necessary to extract the lat/lon information from the graph vertices and put it into a SpatialPoints object for the vertices, and a SpatialLinesDataFrame object for the edges.

此代码为以下示例生成一个非常简单的 igraph 对象:

This code produces a very simple igraph object for the following example:

library(igraph)

## Produce a ring graph with 4 vertices
x <- graph.ring(4)

## Add lat/lon information to vertices
V(x)$lat <- c(50, 50, 51, 51)
V(x)$lon <- c(40, 41, 41, 40)

现在，为顶点创建 SpatialPoints 对象

Now, create the SpatialPoints object for the vertices

library(sp)
library(maptools)

## Create SpatialPoints object containing coordinates
xV <- SpatialPoints(cbind(V(x)$lon, V(x)$lat))

## Write vertices to a shapefile
writePointsShape(xV, fn="vertices")

最后，为边创建 SpatialLinesDataFrame 对象.这有点乱，但我还没有找到一种快速的方法来生成给定坐标的 SpatialLines 对象.

Finally, create the SpatialLinesDataFrame object for the edges. This is a little messy, but I am yet to find a quick way to produce a SpatialLines object given coordinates.

## Create SpatialLinesDataFrame object describing edges
edges <- get.edgelist(x)+1
edges <- cbind(edgeNum=1:nrow(edges), v1=edges[,1], v2=edges[,2])
xE <- apply(edges, 1, function(i) Lines(Line(cbind(c(V(x)$lon[i["v1"]], V(x)$lon[i["v2"]]), c(V(x)$lat[i["v1"]], V(x)$lat[i["v2"]]))), ID=as.character(i["edgeNum"])))
xE <- SpatialLinesDataFrame(SpatialLines(xE), data=data.frame(edgeNum=1:nrow(edges)))

## Write edges to a shapefile
writeLinesShape(xE, fn="edges")

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